On Friday 26 June 2009 02:07:58 terryc wrote:
> Silver Salonen wrote:
> >  Eg. if we want to do ordinary Grandfather-Father-Son rotation, we 
> > create 3 different pools for every job - for full, differential and 
> > incremental backups.
> 
> That is not how I understand GFS system, although it is a possibility. I 
> understand it as Full, plus (incremental OR differential).
> 
> So important clients (like secretary's machine) receive a full backup 
> each week and a differential (all changed files since full backup) 
> nightly so that in the need for recovery, it would just be a process 
> involving two tape/disk(?) for a full recovery.
> 
> OTOH, I might do a differential (all changed files since last backup, 
> full or diff or inc) on something on something with humungous amount of 
> file changes and non-core/non-critical files to simply keep the backup 
> window small. The trade off is that every tape/disk since the full 
> backup would need to be processed for a full client recovery.
> 
> GFS comes from having multiple complete BACKUPS, i.e. dated versions. 
> This makes it a real backup system.

OK, yes.. you may do it as this too, but the point in this context was that we 
need multiple pools. In my case I need one pool for full backups, one for 
differentials and one for incrementals. In your case you need 2 pools: one for 
fulls and one for differentials.

> > Using only one pool with the whole backup-disk doesn't make sense to me, 
> > because managing these backups would be extremely limited, wouldn't it?
> 
> If you want to run your backups like that, then use a raid array. You 
> only have a point in the rare occassions where you have small backups 
> and monstrous drives. The critical point about a real backup system is 
> that it is not just a file copy, but a secure,protected file copy that 
> can not be degraded. Writing a whole serious of jobss to one drive that 
> sits in the system full time is not a proper backup system.

Well.. I AM using RAID array everywhere in backup-systems and as it's so much 
more cost effective than using tapes, we just hope we can detect any soon-to-
failure storage soon enough :)

--
Silver

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